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The FBI said Friday that white powder found at New Jersey hotels near the site of the Super Bowl and at the Manhattan office of former Mayor Rudy Giuliani proved to be non-hazardous.

Hazardous materials teams and bomb squads responded after white powder was found at several hotels near New Jersey's MetLife Stadium, authorities said.

In a statement late Friday, the New Jersey State Police said most of the locations that the Joint Terrorism Task Force and hazard materials responded to because of the suspicious powder had been secured. No injuries were reported.

The FBI In New York tweeted Friday afternoon: "Substances in suspicious letters in New York and New Jersey deemed non hazardous. Additional testing to come."

The contents of one letter sent to the Homewood Suites in East Rutherford were tested and determined to be cornstarch, East Rutherford Mayor James Cassella said.

A New York police spokesman said the letter sent to Giuliani's office contained a "nontoxic substance." Still, eight employees in the mail room were decontaminated as a precaution, and no one has shown any sign of illness, he said.

Giuliani told CNN's Wolf Bitzer on The Situation Room that the letter with white powder was addressed to his administrative assistant.

"Of course, it created tremendous concern," he said. "But the police department showed up. My firm . ... is a security firm, thank goodness, so they knew how to handle it immediately. They did a a test. The preliminary test is that it's nontoxic... We don't know if it's connected to the six or seven that were sent in New Jersey."

He added, "It's kind of a strange letter, more than a threatening letter. Said something about 'you're being my best friend' and this person is not my best friend or my assistant's best friend, or anyone we know. ... At this point, all we know is the good news is it's not toxic. The bad news is we don't really know if it's connected."

The letter was postmarked from Toronto, Ontario, and contained a name and return address. New York law enforcement authorities were in touch with Canadian authorities to pursue the source of the letter, police said.

In New Jersey, Hackensack University Medical Center evaluated some people who may have come in contact with the suspicious letters, a State Police spokesman said. No illnesses or injuries were reported.

In a statement, the FBI said earlier Friday: "The Joint Terrorism Task Force and Hazard Materials units have responded to several locations that have received a suspicious letter and substance. There are no reported injuries at this time, and the locations are being secured."

The scares come amid tight security before Sunday's game. More air marshals and behavioral detection officers, radiological detection teams and random baggage checks at transit hubs are among the security measures the federal Homeland Security Department deployed to help local police in New Jersey and New York secure the Super Bowl.

The stadium's location near a major airport and busy commuter train lines presents security challenges. Unlike audiences for other championship games, spectators of Super Bowl XLVIII will rely heavily on mass transit.

Chris Murray, business management president at the Quality Inn in Lyndhurst, said the hotel received a suspicious letter but he did not know what was inside the envelope. He said local police were at the hotel and that a Hazmat team and bomb squad were expected to examine the letter.

Murray said other hotels on the same corner in Lyndhurst also received suspicious envelopes, including the Renaissance and Marriott Courtyard.

The letter was sitting on a desk in his office, Murray said.

Other hotels that received suspicious packages included the Econo Lodge, Holiday Inn and Hampton Inn in Carlstadt, and Renaissance Inn and Homestead in Rutherford.

Law enforcement officials said six letters were discovered in New Jersey.